1(34 Ulothricaceae 



more, physiologically it behaves like other species of Stichococcus, 

 in that its cell-walls do not become gelatinous like those of Ulo- 

 tJirix when kept in stagnant cultures. In describing the species 

 under this genus, Klercker identified it with hesitation with Kiitz- 

 ing's UlotJirix subtilis, but in our judgment the figure furnished by 

 Kiitzing makes the identification as certain as in the case of most 

 of our species of that date. 



Of the eight or more varietal forms that have accumulated 

 about Ulothrix subtilis from the time of Rabenhorst down to Hans- 

 girg, at least three (viz., variabilis, stagnorum and tencrrimd) 

 belong to other genera than SticJwcoccus ; it is doubtful whether 

 some of the rest can be placed in close relation with this species 

 as here interpreted, even if they are to be brought into the genus. 



The form illustrated by Kiitzing (Tab. Phyc. 2 : 31.//. 97- f- 4- 

 •1852) under the name Ulothrix rupicola Bailey, but apparently 

 never described, appears both from the figure and from an authen- 

 tic specimen furnished by Mr. Collins, to be simply Stichococcus 

 subtilis. 



5. Stichococcus flaccidus (Kiitz.) Gay, Rech. sur Alg. Vert. 



79. pi. 11. f. 1 01-106. 1 89 1. Klercker, Flora, 82: 104. 



1896. De Wild. Flor. Alg. Belg. 94. /. 42. 1896. 



Ulothrix flaccida Kiitz. Spec. Alg. 349. 1849; Tab. Phyc. 2: 

 //. 05. f. 2. 1852. Rabenh. Flor. Eur. Alg. 3: 367. 1868. 

 Wolle, F. W. Alg. 137. //. 118. f. 27, 28. 1887. De Wild. 

 Bull. Soc. Bot. Belg. 2f : 79-81. 1888. 



Hormidium flaccidum Braun ; Rabenh. Alg. Eur. 2480. 1876. 

 Klebs, Fortpflanz. Einig. Alg. 341-345. //. 2. f. 21-24. 1896. 



Hormiscia flaccida Lagerh. Flora, 71: 62. 1888. Hansg. 

 Flora, 71: 265. p. p. 1888. DeToni, Syll. Alg. 1: 161. p. p. 



Hormococcus flaccidus a flaccida \_sic~] Chodat, Beitr. Krypt. 

 Flor. Schweiz, I 3 : 269. 1902. 



Filaments rather short, forming floccose masses or interwoven 

 strata: cells generally somewhat tumid, 6-9. 5 fx (6-14/1, Gay) in 

 diameter, y^-2 times as long : cell-wall thicker than in 5. subtilis ; 

 chromatophore broad, containing a large pyrenoid. 



Reproduction by zoospores, as well as by the vegetative mode, 

 frequent (pi. 21, f. 14-17). 



